Without a laboratory handy, I don't believe that most of us can really tell when "conversion is complete." If you're talking about the iodine test being negative, that's one thing. There are some sugars in there that need to be degraded that nobody seems to either know about or want to talk about. I haven't stopped a mash at 60 min. for probably 15 years. If you want a balanced beer, you need to start with a balanced wort. Of course, watch your temps. but run that mash for at least 2 hours. Magically, you'll see your efficiency go up! Try to keep in mind that it isn't squeezing every morsel of sugar out of that grain to save yourself money, the idea is to take control of your brewhouse.